1. Field of the Invention
The invention relates to a method and an apparatus to regulate the supply of energy to an electric drive and other loads using a hybrid energy supply system that comprises a fuel cell and an energy storage buffer, whereby a vehicle control unit regulates the drive power or drive current required by the drive—which is supplied by a power converter—dependent on a throttle position detected by a detector, which determines the energy required by the drive. For the purposes of this invention, the term vehicle also includes other mobile devices, such as for example boats or airplanes.
2. Description of the Related Art
Known in the art is an energy supply system in a vehicle including a fuel cell consisting of individual fuel cell modules and a storage battery that may be connected in parallel to the output of the fuel cell. The fuel cell is supplied with hydrogen-containing fuel from a reformer and with air from a compressor. The reformer receives methanol from a tank and water from a further tank and generates the hydrogen-rich fuel by way of steam reforming. A DC/DC converter, which supplies a drive motor, is connected to receive power from the fuel cell. The drive motor is connected to a control system, which is connected to a sensor indicating the throttle position. Furthermore, the control system is also connected to a control unit for the hybrid energy supply system, which comprises the fuel cell, the reformer, common auxiliaries for the operation of the fuel cell, and the storage battery (DE 197 31 250 A1).
Also known in the art is a hybrid energy supply system to supply an electrical load comprising a fuel cell and a storage battery that is connected to the electrical outputs of the fuel cell, whereby the battery's state of charge is monitored. A control system ensures that after each discharge event the storage battery is recharged in as little time as possible and is available to assist the fuel cell in supplying power to the load (EP 33 44 74 B1).
Also known in the art is a fuel cell arrangement comprising a fuel cell that is supplied by a methanol reformer, and a parallel-connected storage battery, whereby a voltage-amplifier adapter is arranged between the outputs of the fuel cell and the storage battery. The fuel cell system supplies power to a speed control unit with a connected motor. The charge state of the storage battery is monitored. The battery compensates for transient variations in the power output of the fuel cell. The fuel cell operates in a load range with favorable efficiency and—if required—charges the storage battery via the appropriately set voltage-amplifier adapter (U.S. Pat. No. 6,214,484 B1).
In a known fuel-cell-powered energy generating system with a storage battery and a strongly variable electrical load, the charge state of the storage battery, which is connected in parallel to the load, is monitored and compared to a target charge state. In order to maintain the charge state at a preset minimum level, the supply of reactant gases to the fuel cell is increased if so required and a DC/DC converter that is connected on the load side of the fuel cell is regulated appropriately (Patent Abstracts of Japan, Publication Number 0121 18600 A).
In a further known fuel-cell-powered energy generating system, which comprises a fuel cell and a storage battery that is connected in parallel to the fuel cell, the charge state of the battery is monitored. When the energy generating system is powered up, a controller estimates the electrical power requirements of the common auxiliaries by way of the charge state and the gas supply to the fuel cell is adjusted in dependence on this estimate (U.S. Pat. No. 5,964,309).
Also known in the art is a fuel cell system in which a DC/DC converter is connected to the electrical outputs of the fuel cell, whereby the outputs of the DC/DC converter are connected to a battery and an inverter, which supplies power to a motor. A control unit calculates the required power output of the inverter based on the request of an acceleration setpoint generator, determines a high-efficiency operating point for the fuel cell from the characteristic curve of the output voltage of the fuel cell as a function of the output current, and adjusts the power output of the fuel cell and the level of the output voltage of the DC/DC converter so that the power required by the inverter will be supplied by the fuel cell and the battery (WO 99/67 846).
Also known in the art is a motor vehicle that can be driven by an electric motor and includes an energy storage device to supply electrical loads, additional energy sources such as an internal combustion engine, generators, or photovoltaic cells, and a control unit working as energy managing device. The control unit distributes the energy from the energy sources to the electrical loads, if the loads require energy (DE 196 17 548 A1).
Further known in the art is an energy-generating device with a fuel cell in a vehicle, which is equipped with a traction motor, which is connected via a converter to a high-voltage network that is supplied with power by the fuel cell. An on-board low-voltage network includes loads, such as lamps, windshield-wiper motors, etc., and a battery, and is connected to the high-voltage network via a DC/DC converter. Also present is an energy storage buffer, which supplies the energy for the start-up of the fuel cell and is charged during the operation of the fuel cell. In the event of elevated power requirements, the energy storage buffer delivers power to the loads and is charged during braking (WO 01/34424 A1).
Also known in the art is a power-regulating system for motor vehicles that contain an internal combustion engine and a multitude of power-converting components, the individual efficiencies of which can be determined. An overall efficiency is calculated from these individual efficiencies. One parameter for each of the respective components is adjusted to achieve an optimum overall efficiency. In particular, these parameters may include the power output or a variable that is proportional thereto, and/or the rotational speed (DE 195 05 431 A1).